Method to eliminate the noise at known frequency

Abstract

In measurement of signals containing noise at a known frequency, a method to eliminate noise at a known frequency of T so adapted as to obtain correct value of the signal free from noise by repeating measurements of signal levels at time interval of T/2 and averaging the values obtained by said measurements.

We claim: 
     
       1. In measurement of signals containing noise at a known frequency, a method for eliminating the noise comprising the steps of measuring the signals an even number of times at time intervals equal to odd multiples of half the period of the noise, and automatically calculating an average of the measured values obtained by said measurements. 
     
     
       2. In measurement of signals containing noise at a known frequency, a method for eliminating the noise comprising the steps of measuring the signals an even number of times at time intervals equal to half the period of the noise, and automatically calculating an average of the measured values obtained by said measurements. 
     
     
       3. In measurement of signals containing noise at a known frequency, a method for eliminating the noise comprising the steps of measuring the signals twice at a time interval equal to odd multiples of half the noise period, and automatically calculating the measured values obtained by said measurements. 
     
     
       4. In measurement of signals containing noise at a known frequency, a method for eliminating the noise comprising the steps of measuring the signals twice at a time interval equal to half the noise period, and automatically calculating an average of the measured values obtained by said measurements. 
     
     
       5. In combination, apparatus for eliminating noise having a known frequency from signals, comprising an amplifier for amplifying measured output signals, an A/D converter for converting the signals provided from said amplifier into digital signals, a pulse generator for generating pulses at time intervals equal to half the noise period and a circuit for calculating an average.